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If I try to put a date field in a Document (BSON) and write it to Mongo, BSON writes it in UTC. For example, a date 

DateTime dateTime = new DateTime("2015-07-01");
Document doc = new Document("date", dateTime.toDate());

will be stored as 

"date" : ISODate("2015-06-30T18:30:00Z")

in Mongo. And, if I retrieve it using the same Java Driver I get it as 

Wed Jul 01 00:00:00 IST 2015

Great. Is there no solution to this? I mean, why can't I store my date as I want it? What If I need to query on the DB from another time zone? I will be getting different results? Date field is an important part of Mongo with a rich set of operators wrapped around it. Still, why doesn't Mongo provide this flexibility? Thanks

void
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  • "What If I need to query on the DB from another time zone?" What exactly do you mean? Basically, the `Date` type represents an instant in time, internally stored as milliseconds since the Unix epoch. If you don't want to store an instant in time, `Date` isn't going to help you :( – Jon Skeet Jul 27 '15 at 13:38
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    Well, in general it's better to keep dates as UTC in database already. Maybe you should do timezone staff in your api side. – Sercan Ozdemir Jul 27 '15 at 13:41
  • @JonSkeet I have inserted the date field from IST zone. What If I need to query the DB from a different time zone? Won't I be getting the corresponding date-time in that time zone? How can I store the date as it is? – void Jul 27 '15 at 13:42
  • Just repeating "What If I need to query the DB from a different time zone?" doesn't actually tell me what you mean by that. The date value doesn't have any knowledge of a time zone - it's just an instant in time. Likewise any query you perform will just compare that value with another instant in time. I don't know what you mean by "as it is" in this case, but you need to understand what the `Date` type means. It's not clear what behaviour you're trying to achieve. – Jon Skeet Jul 27 '15 at 13:43
  • @JonSkeet Maybe the instant-in-time storage is causing my problem. I need to store the date as "2015-07-01". And would like to query for the same from India or London and get the result as "2015-07-01" in both cases. Maybe Mongo isn't my use-case db :( – void Jul 27 '15 at 13:51
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    Indeed - you'll either have to store it as a different type, or parse your original date/time in UTC (i.e. store 2015-07-01T00:00:00Z). – Jon Skeet Jul 27 '15 at 14:02

5 Answers5

4

IMO, mongo did everything right. You instantiate date using your local timezone and then store it in mongo in UTC. And then when you ask mongo to retrieve it for you it shifts date to your local timezone again.

If you dont want to deal with timezone shifting, just set your local timezone to UTC using the following flag:

-Duser.timezone="UTC"
Alex
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    @AswinJoseRoy set this as your apllication launch parameters i.e. `java -jar yourApp.jar -Duser.timezone="UTC"` – Alex Jul 28 '15 at 05:53
  • IMO mongo did not do everything right. I want to persist a day. Meaning a day in time. I don't want to persist a point in time, that is represented at different days depending on the timezone. If I want to do that, I store a Time object. – Ekkstein Feb 09 '22 at 21:16
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    @Ekkstein Sorry, that's not what the `datetime` does... in Python or BSON. It doesn't store a `date`, it doesn't store a `timeoffset` or anything else. You are asking for a datatype that is just not naturally supported in BSON. The good news is: you can roll your own. Use a string. Use an integer. Use an object like `{"$date": "2022-02-09"}`. – Dan H Jul 16 '22 at 01:46
1

When using DateTime (from org.joda.time or java.time) a date with time zone is created and MongoDB has unfortunately no support for it. (see BSON Types)

Therefore persisting it in UTC is a easy and reliable solution without loosing any data.

As a alternative you should take a look at LocalDateTime. It contains no DateTimeZone and so nothing has to be converted first.

TAL
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0

I have the problem solved by setting my timezone as UTC from within the code itself. 

    DateTimeZone zone = DateTimeZone.UTC;
    DateTimeZone.setDefault(zone);
void
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0

Got a very simple solution. Let the date be in UTC in your MongoDB.
Whenever you fetch it to your UI, just do: 

new Date(fetchedDate);

It converts it to the local date.

סטנלי גרונן
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user42344
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0

I was facing the same issue while retrieving the date from MongoDB. MongoDB follows the UTC timezone that's why when you perform any date operations, it converts into UTC.

So I used post hook from mongoose to convert the date and time in my preferable timezone. Here is the snippet.

schema.post(['find', 'findOne'], async function(docs, next) {
    docs.map((doc) => doc.createdAt= convertToTz({tz: process.env.TZ, date: doc.createdAt}))
    next();
});

Here, createdAt is the date when the document is created. convertToTz is a common function that I mentioned below.

const moment = require("moment-timezone");

const convertToTz = (params) => {
  try {
        let tz = params?.tz ?? process.env.TZ;
        let format = params?.format ?? "";
        return moment(params.date).tz(tz).format(format);
    } catch (error) {
       throw new Error(error);
  }
};

NOTE: This code is in NodeJs but I hope this will solve your problem.

Vaibhav Tamakuwala
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